/*
 ***************************************************************************************
 *  Copyright (C) 2006 EsperTech, Inc. All rights reserved.                            *
 *  http://www.espertech.com/esper                                                     *
 *  http://www.espertech.com                                                           *
 *  ---------------------------------------------------------------------------------- *
 *  The software in this package is published under the terms of the GPL license       *
 *  a copy of which has been included with this distribution in the license.txt file.  *
 ***************************************************************************************
 */
package com.espertech.esper.common.internal.epl.historical.lookupstrategy;

import com.espertech.esper.common.client.EventBean;
import com.espertech.esper.common.internal.epl.expression.core.ExprEvaluatorContext;
import com.espertech.esper.common.internal.epl.index.base.EventTable;

import java.util.Iterator;

/**
 * Strategy for use in poll-based joins to reduce a cached result set (represented by {@link EventTable}), in
 * which the cache result set may have been indexed, to fewer rows following the join-criteria in a where clause.
 */
public interface HistoricalIndexLookupStrategy {
    /**
     * Look up into the index, potentially using some of the properties in the lookup event,
     * returning a partial or full result in respect to the index.
     *
     * @param lookupEvent provides properties to use as key values for indexes
     * @param index       is the table providing the cache result set, potentially indexed by index fields
     * @param context     context
     * @return full set or partial index iterator
     */
    Iterator<EventBean> lookup(EventBean lookupEvent, EventTable[] index, ExprEvaluatorContext context);
}
